1. Technical Field
The present invention relates to a tool and an apparatus for shaping soft materials, such as a foam material, and more particularly, to a heating tool which a surface of a workpiece melted rapidly and the molten surface has thermally decomposed.
2. Description of the Related Art
Generally, methods of shaping soft materials, such as a foam material, may be classified into two types: a method of cutting the soft material using a cutting tool, and a method of melting a soft material by using a heating tool.
The cutting method using the cutting tool always generates chips during a cutting process. The chips may be scattered about a shaping apparatus, but most of the chips are built up on a cutting path, thereby hindering the movement of the cutting tool. Thus, this method has a problem in that the precision becomes low. In order to solve the problem, U.S. Pat. No. 6,234,725 discloses that an evacuation bore drawing air is provided on a predetermined portion of the cutting tool. The evacuation bore draws the chips generated during the cutting process along with the air. Such a method allows the chips to be easily evacuated, but is disadvantageous in that a chip removal rate is not high, so that a working environment is not greatly improved. Further, the evacuation bore may cause a defect on a surface of a workpiece.
To the contrary, the melting method using the heating tool shapes a soft material by melting the soft material and does not generate the cutting chips. The method using the heating tool is found in Korean Patent Laid-open Publication No. 2003-4638 and Korean Patent Application No. 2003-47255, which are incorporated herein by reference.
FIG. 1 shows a conventional heating tool used for the melting method. As shown in FIG. 1, the conventional heating tool 10 is provided with a very thin hot wire 11. The hot wire 11 generates heat with a high temperature of 700° C. or higher, when a voltage is applied to the heating tool 10. Thus, when the hot wire 11 approaches workpiece made from a soft material, a surface of the workpiece is melted by radiant heat emitted from the hot wire 11. Such method has an advantage in that the workpiece can be shaped without coming in direct contact with the heating tool 10. As a result, there is no cutting resistance due to contact friction between the workpiece and the heating tool 10. Further, the shaping method has another advantage in that the hot wire is thin and radiant heat is restricted within a narrow range, thus ensuring a more precise shaping, as compared to the former method using the cutting tool.
However, the conventional heating tool has a problem in that thermal energy is transmitted to the workpiece via the hot wire having a very small surface area, so that the shaping process takes a long time. Thus, when such a heating tool is used at a preliminary shaping stage in which a large area is processed, only a localized part of a workpiece is thermally decomposed, and a large part of the workpiece remains molten. Further, the molten material may be adhered to the workpiece or the heating tool, thus deteriorating a surface roughness of the workpiece and lowering precision of the heating tool. Accordingly, there is a need to provide a heating tool for shaping soft materials, capable of rapidly shaping a large area of a workpiece without generating cutting chips. There is also a need to provide a shaping apparatus using the heating tool, which is capable of shaping a workpiece in three dimensions using the heating tool.